Method for ejecting a test strip from a test meter

ABSTRACT

A method for ejecting a test strip from a test meter includes initiating activation of a test strip ejection mechanism that is in a pre-ejection state. In the method, the test strip ejection mechanism includes a shape memory alloy strip that exhibits a solid state transition temperature and has a programmed configuration and a deformed configuration. In the test strip ejection mechanism pre-ejection state, a test strip has been received within a test strip receiving port of the test meter and the shape memory alloy strip is in the deformed configuration. The method also includes heating, in response to the initiation step, the shape memory alloy strip from below the solid state transition temperature to above the solid state transition temperature. The heating results in the shape memory alloy strip undergoing a transformation from the deformed configuration to the programmed configuration. The method also includes applying a force produced by the transformation from the deformed configuration to the programmed configuration to the test strip and, thereby, ejecting the test strip from the test strip receiving port.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to medical devices and, inparticular, to test strip ejection mechanisms, related test meters andrelated methods.

2. Description of Related Art

The determination (e.g., detection and/or concentration measurement) ofan analyte in a fluid sample is of particular interest in the medicalfield. For example, it can be desirable to determine glucose, ketones,cholesterol, acetaminophen and/or HbAlc concentrations in a sample of abodily fluid such as urine, blood or interstitial fluid. Suchdeterminations can be achieved using analyte test strips, based on, forexample, photometric or electrochemical techniques, along with anassociated test meter.

During use, a single test strip is typically inserted into a test meter.

Following determination of an analyte in a bodily fluid sample appliedto the test strip, the test strip is removed from the test meter anddiscarded. Conventional approaches to inserting and removing a teststrip from a test meter are described in, for example, U.S. Pat. Nos.5,266,179; 5,366,609; and 5,738,244; and U.S. Patent ApplicationPublication 2009/0108013, each of which is hereby incorporated in fullby reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings, in which like numerals indicate like elements, ofwhich:

FIG. 1 is a simplified exploded view of a test strip ejection mechanismaccording to an embodiment of the present invention in use with a teststrip receiving port assembly and optical module of a test meter and atest strip;

FIGS. 2A, 2B and 2C are simplified top, side and bottom views of thetest strip ejection mechanism of FIG. 1 in use with the test stripreceiving port assembly, optical module and test strip of FIG. 1;

FIG. 3 is a simplified perspective view (from the bottom) of test stripejection mechanism of FIG. 1 in a pre-ejection state with the test stripreceiving port assembly, optical module and test strip of FIG. 1;

FIG. 4 is a simplified perspective view (from the bottom) of test stripejection mechanism of FIG. 1, with the test strip receiving portassembly, optical module and test strip of FIG. 1, during ejection ofthe test strip;

FIG. 5 is a simplified perspective view (from the bottom) of test stripejection mechanism of FIG. 1, with the test strip receiving portassembly, optical module and test strip of FIG. 1, following ejection ofthe test strip and deformation of the shape alloy memory strip;

FIG. 6 is a simplified block diagram of a test meter according to anembodiment of the present invention; and

FIG. 7 is a flow diagram depicting stages in a method for ejecting atest strip from a test meter according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following detailed description should be read with reference to thedrawings, in which like elements in different drawings are identicallynumbered. The drawings, which are not necessarily to scale, depictexemplary embodiments for the purpose of explanation only and are notintended to limit the scope of the invention. The detailed descriptionillustrates by way of example, not by way of limitation, the principlesof the invention. This description will clearly enable one skilled inthe art to make and use the invention, and describes severalembodiments, adaptations, variations, alternatives and uses of theinvention, including what is presently believed to be the best mode ofcarrying out the invention.

In general, a test strip ejection mechanism, for use with a test stripreceiving port and a test strip, includes a framework, an elongatedshape memory alloy (SMA) strip (e.g., a SMA wire), a slider, and aheating module. The SMA strip has first and second ends that areattached to the framework and exhibits a solid state transitiontemperature. The slider is configured to travel along the framework.

The heating module is configured to heat the SMA strip from atemperature below the solid state transition temperature to atemperature above the solid state transition temperature. Moreover, theSMA strip and slider are configured such that the slider travels alongthe framework under an applied force exerted on the slider by the SMAstrip as the SMA strip is heated from a temperature below the solidstate transition temperature to a temperature above the solid statetemperature. In addition, the slider has a proximal end configured toengage a test strip received within a test strip receiving port andeject the test strip from the test strip receiving port as the slidertravels along the framework.

Shape memory alloys (SMA) are materials that that transform from adeformed shape (also referred to herein as a “deformed configuration”)to an original shape (also referred to herein as a “programmedconfiguration”) upon heating to a temperature above their solid-statetransformation temperature. This behavior is also referred to asreturning to their original shape (programmed configuration).

At temperatures below the solid state transformation temperature, theshape memory alloy Nitinol is in the martensite phase. To set a NitinolSMA strip (e.g., a Nitinol SMA wire) to a predefined “programmedconfiguration” or programmed state, the SMA strip is held in theprogrammed configuration and heated to approximately 500° C., at whichtemperature atoms of the SMA strip arrange themselves into the austenitephase. Thereafter, when heated above the solid state transitiontemperature, the Nitinol SMA wire will automatically revert from themartensite phase to the austenite phase, which acts to change the shapememory alloy (via a solid-state phase transition) from any deformedconfiguration back into the programmed configuration. In other words,the shape memory alloy strip changes shape in response to temperature.During such a transformation, the SMA exerts a smooth and controlledforce that is employed in embodiments of the present invention to ejecta test strip.

Once apprised of the present disclosure, one skilled in the art willrecognize that there are a variety of shape memory alloys that may besuitable for use test strip ejection mechanisms according to embodimentsof the present invention depending on their solid state transitiontemperature and mechanical properties. Known shape memory alloymaterials include, for example:

Nickel/Titanium alloys (including Nickel/Titanium alloys commerciallyavailable as Nitinol and Tinel);

Copper/Zinc/Aluminum alloys

Copper/Aluminum/Nickel alloys

Silver/Cadmium alloys

Gold/Cadmium alloys

Copper/Tin alloys

Copper/Zinc alloys

Indium/Titanium alloys

Nickel/Aluminum alloys

Iron/Platinum alloys

Manganese/Copper alloys

Iron/Manganese/Silicon alloys

Test strip ejection mechanisms according to embodiments of the presentinvention are beneficial in that they operate automatically. In otherwords, they operate with minimal human intervention, in the absence ofhuman energy (as opposed to conventional manual ejection mechanisms) andin a manner essentially independent of external influence or control.Test strip ejection mechanisms according to embodiments of the presentinvention also beneficially provide test strip ejection without the needfor human handling of, and potential contamination from, the test strip.The test strip ejection mechanisms are also compact and relatively quietdue to the absence of ejection-related motors and/or gears and are,therefore, suitable for incorporation into handheld portable test meters(such as test meters for the determination of glucose).

FIG. 1 is a simplified exploded view of a test strip ejection mechanism100 according to an embodiment of the present invention in use with atest strip receiving port assembly 200 and optical module 300 of anassociated test meter and a test strip TS. FIGS. 2A, 2B and 2C aresimplified top, side and bottom views of test strip ejection mechanism100 in use with test strip receiving port assembly 200, optical module300 and test strip TS. FIG. 3 is a simplified perspective view (from thebottom) of test strip ejection mechanism 100 in a pre-ejection state(for example, following strip insertion and analyte determination). FIG.4 is a simplified perspective view (also from the bottom) of test stripejection mechanism 100 during ejection of test strip TS with the shapememory alloy strip in a programmed configuration. FIG. 5 is a simplifiedperspective view of test strip ejection mechanism 100 following ejectionof test strip TS and return of the shape alloy memory strip to adeformed configuration.

Referring to FIGS. 1, 2A through 2C, 3, 4 and 5, test strip ejectionmechanism 100 is configured for use with test strip receiving portassembly 200 and test strip TS. Test strip ejection mechanism 100includes a framework 102, an elongated shape memory wire 104, a slider106, spring 108, spindle 110, and connector 112 (i.e., a screw andwasher combination). Test strip ejection mechanism 100 also includes aheater module, which for simplicity is not shown in FIGS. 1, 2A through2C, 3, 4 and 5. The heater module can be any suitable heater moduleknown to those of skill in the art including, for example, a heatermodule configured to force a predetermined electrical current throughelongated shape memory alloy wire 104 in a controllable manner and,thereby, heat the elongated shape memory alloy wire.

Test strip receiving port assembly 200 includes a test strip receivingport 202 and test strip receiving framework 204. Optical module 300 isconfigured to sense the presence and absence of a test strip in teststrip receiving port assembly 200. Optical module 300 can be anysuitable optical module known to those of skill in the art and caninclude, for example, a an LED-based light source and a photodiode-basedlight receiver configured to detect the presence or absence of a teststrip based on, for example, the position of an opaque light-blockingfin or reflector optionally included in slider 106. Such detection canbe employed, if desired, to automatically control the deactivation ofelongated shape memory alloy wire 104 and/or to monitor for mechanicalfailures of test strip ejection mechanism 100. Alternatively, a suitablemechanical switch can also be employed to detect the presence or absenceof a test strip based on, for example, the position of slider 106.

As knowledge of the presence or absence of a test strip can be used fortest meter purposes (e.g., to initiate analyte determination by the testmeter) or to conclude (deactivate) heating of an elongated shape memoryalloy wire within the test strip ejection mechanism once a test striphas been ejected, optical module 300 can be considered either acomponent of the test meter or an optional component of the test stripejection mechanism.

Framework 102 is attached to the test strip receiving port assembly 200and includes a slider guide slot 114 and strip attachment slots 116 aand 116 b. Elongated shape memory alloy wire 104 has a longitudinalaxis, a first end 118 a and a second end 118 b. First end 118 a secondend 118 b of elongated shape memory alloy 104 are constrained byattachment to framework 102 via strip attachment slots 116 a and 116 band crimps 120 a and 120 b of elongated shape memory alloy wire 104.

As described above, elongated shape memory alloy wire 104 inherentlyexhibits a solid state transition temperature due to being formed of asuitable shape memory alloy material (e.g., a Nickel/Titanium alloy). Inembodiments of the present invention, the solid state transitiontemperature is typically in a range between 65° C. and 95° C. The lowertemperature of the range is predetermined to be greater than the maximumambient temperature encountered during normal use and the uppertemperature of the range is chosen based on thermal compatibility withmaterials used to construct framework 102, slider 106 and othercomponents of the test strip ejection mechanism (e.g., plasticmaterials). Upon heating above the solid state transition temperature,the shape memory behavior of elongated shape memory alloy wire 104results in a shrinkage ratio in the range of, for example, 1% to 3%.

In test strip ejection mechanism 100, elongated shape memory alloy wire104 has a typical but non-limiting diameter of 0.2 mm and length of 55.8mm and can be constructed of a shape memory alloy containing, forexample, 54% Nickel and 46% Titanium. Such an elongated shape memoryalloy wire can be heated from room temperature to above its solid statetransition temperature with a 3% contraction by, for example, forcing a0.5 amp current through the elongated shape memory alloy wire for a timeduration in the range of approximately 1.0 seconds to 1.2 seconds.

During transition from a deformed configuration to a preprogrammedconfiguration (i.e., upon heating from below the solid state transitiontemperature to above the solid state transition temperature, see FIGS. 3and 4 in particular), this dual-ended constraint of the elongated shapememory alloy wire in conjunction with the deformed configuration of thepre-ejection state and the predefined programmed configuration resultsin the production of a force that is exerted on the slider. The exertionof the force results in test strip ejection.

In the embodiment of FIGS. 1-5, the shape memory alloy wire is in adeformed configuration when the shape memory alloy strip is at atemperature below the solid state transition temperature (e.g., anambient room temperature of approx. 25° C.) and the shape memory alloystrip is in a programmed configuration when the shape memory alloy stripis heated to a temperature above the solid-state transition temperature(for example, above 65° C.). In addition, in the embodiment of teststrip ejection mechanism 100, the longitudinal axis of the shape memoryalloy wire in the deformed configuration is in essentially anequilateral obtuse-angled triangle configuration (see FIGS. 1, 2C, 3 and5) and the longitudinal axis of the shape memory alloy strip in theprogrammed configuration is in an essentially straight-lineconfiguration (see FIG. 4) perpendicular to a test strip ejectiondirection. These predefined configurations serve to produce a smoothlinear movement in the slider during ejection of a test strip.

The equilateral obtuse-angled triangle configuration of the shape memoryalloy wire is a “bowed” configuration that transitions to astraight-line configuration while functioning to push slider 106 andeject a test strip. These configurations and functions are reminiscentof the configuration and function of a bow and arrow. In a bow and arrowanalogy, which is presented for non-limiting descriptive purpose only,the framework and elongated shape memory alloy wire are reminiscent ofthe bow and bow string, while the slider and test strip are reminiscentof the arrow. However, once apprised of the present disclosure, oneskilled in the art will recognize that test strip ejection mechanismsaccording to embodiments of the present invention operate automatically,beneficially employ shape memory alloy behavior and have other unique,non-obvious and beneficial aspects that differ from a conventional bowand arrow.

In the embodiment of test strip ejection mechanism 100, slider 106 isconfigured to travel along framework 102 in slider guide slot 114 (seeFIG. 1 in particular) and provides a mechanical connection betweenelongated shape memory alloy wire 104 and test strip TS. In particular,slider 106 has a proximal end 107 configured to engage test strip TSreceived within test strip receiving port 202 and eject test strip TSfrom test strip receiving port 202 as slider 106 travels along framework102 (see FIGS. 3, 4 and 5 in particular). The distance of slidermovement during ejection of a test strip is, for example, in the rangeof 4 mm.

Spring 108 and spindle 110 are configured to return and hold the shapememory alloy strip in a deformed configuration when the shape memoryalloy strip is at a temperature below the solid state transitiontemperature (see FIGS. 3 and 5 in particular) and enable the shapememory alloy strip to move to a programmed configuration when the shapememory alloy strip is heated to a temperature above the solid-statetransition temperature (see FIG. 4 in particular). Spring 108 andspindle 110 can be configured to exert suitable operational forces onthe elongated shape memory alloy wire during operation of test stripejection mechanism 100. For example, a force of approximately 1 N in anearly unloaded state and a maximum force of 3.2 N during compression ofspring 108 can be exerted during operation. Connector 112 is configuredto hold (along with spring 108 and strip attachment slots 116 a and 116b) elongated shape memory alloy wire 104 in the deformed configurationon framework 102. Connector 112 also provides mechanical contact betweenelongated shape memory alloy wire 104 and slider 106.

The heating module (not depicted in the FIGs.) of test strip ejectionmechanism 100 is configured to heat the shape memory alloy strip from atemperature below the solid state transition temperature to atemperature above the solid state transition temperature. Such heatingcan be accomplished, be employing a heating module that forces anelectrical current through the shape memory alloy wire with the heatingoccurring as a consequence of electrical resistive thermal effects.

In test strip ejection mechanism 100, elongated shape memory alloy wire104 and slider 106 are configured such that slider 106 travels alongframework 102 under an applied force exerted on slider 106 by elongatedshape memory alloy wire 104 as the shape memory strip is heated by theheating module (not shown). The heating raises the temperature of theelongated shape memory alloy wire 104 from a temperature below the solidstate transition temperature (e.g., ambient room temperature) to atemperature above the solid state temperature.

A benefit of test strip ejection mechanisms according to embodiments ofthe present invention is that there is no need to include mechanismsthat translate a rotational movement into a linear test strip ejectionmovement. Test strip ejection mechanisms according to embodiments of thepresent invention are also beneficially thin; lightweight; low cost,relatively silent and eject test strips in a smooth manner.

In general, test meters for use with a test strip (e.g., a test stripconfigured for the determination of glucose in a whole blood sample byphotometric or electrochemical-based techniques) according toembodiments of the present invention include a test strip receiving portand a test strip ejection mechanism. Moreover, the test strip ejectionmechanism includes a framework, an elongated shape memory alloy (SMA)strip, a slider, and a heating module.

The SMA strip of the test strip ejection mechanism has first and secondends that are constrained by attachment to the framework and the SMAstrip exhibits a solid state transition temperature. Moreover, theslider is configured to travel along the framework and the heatingmodule is configured to heat the SMA strip from a temperature below thesolid state transition temperature to a temperature above the solidstate transition temperature. In addition, the SMA strip and slider areconfigured such that the slider travels along the framework under anapplied force exerted on the slider by the SMA strip as the shape memorystrip is heated from a temperature below the solid state transitiontemperature to a temperature above the solid state temperature by theheating module. In addition, the slider has a proximal end configured toengage a test strip received within a test strip receiving port andeject the test strip from the test strip receiving port as the slidertravels along the framework.

FIG. 6 is a simplified block diagram of a test meter 600 according to anembodiment of the present invention. Test meter 600 includes a housing602, a test strip receiving port 604 configured to receive, and haveejected therefrom, a test strip (TS), a test strip ejection mechanism606 (for example, test strip ejection mechanism 100 as described withrespect to FIGS. 1, 2A-2C, 3, 4 and 5) and a signal processing module608.

Test strip ejection mechanism 606 includes the following components (notshown in FIG. 6) as described elsewhere herein: (i) a framework attachedto test strip receiving port 604; (ii) an elongated shape memory alloystrip with a longitudinal axis, a first end and a second end, the firstend and second end attached to the framework; (iii) a slider configuredto travel along the framework; and (iv) a heating module configured toheat the shape memory alloy wire from a temperature below the shapememory alloy's solid state transition temperature to a temperature abovethe shape memory alloy's solid state transition temperature.

In addition, and as described further elsewhere herein, the shape memoryalloy strip and slider are configured in a manner that the slidertravels along the framework under an applied force, with the appliedforce being exerted on the slider by the shape memory alloy strip as theshape memory alloy strip is heated from a temperature below the solidstate transition temperature to a temperature above the solid statetemperature by the heating module. Moreover, the slider has a proximalend configured to engage test strip TS (that has been received withintest strip receiving port 604) and eject test strip TS from test stripreceiving port 604 as the slider travels along the framework.

Signal processing module 608 is configured to measure and process asignal (electrical, optical or a combination thereof) during analytedetermination. One skilled in the art will appreciate that signalprocessing module 608 can include and employ a variety of sensors andcircuits that are not depicted in simplified FIG. 6 during determinationof an analyte.

Test meters according to embodiments of have multiple beneficial andunique characteristics including, for example, (i) being relativelysimple and inexpensive due to the absence of bulky and complicatedmotor-based test strip ejection systems; (ii) automatic ejection of atest strip (i.e., the test strip ejection occurs with minimal or nohuman intervention); (iii) being nearly silent during test stripejection due to a minimum number of moving components; and (iv)providing smooth and controlled ejection of a test strip based oncontrolled shape transformation of a constrained shape memory alloystrip.

In addition, once apprised of the present disclosure, one skilled in theart will recognize that test meters according to embodiments of thepresent invention can incorporate any of the features, components,techniques, benefits and characteristics of test strip ejectionmechanisms and methods for ejecting a test strip from a test meteraccording to embodiments of the present invention and described herein.

FIG. 7 is a flow diagram depicting stages in a method 700 for ejecting atest strip from a test meter according to an embodiment of the presentinvention. At step 710 of method 700, activation of a test stripejection mechanism of a test meter that is in a pre-ejection state isinitiated. In method 700, the test strip ejection mechanism includes ashape memory alloy strip that exhibits a solid state transitiontemperature. Moreover, the shape memory alloy strip (e.g., a shapememory alloy wire made of a Nickel-Titanium shape memory alloy) has aprogrammed configuration and a deformed configuration. In addition, inthe test strip ejection mechanism pre-ejection state, a test strip(e.g., a test strip configured for the determination of glucose in awhole blood sample) has been received within a test strip receiving portof the test meter and the shape memory alloy strip is in the deformedconfiguration.

The initiating step can be accomplished, for example, by a user pressingan initiating button of the test meter or by suitable electronic modulesand/or software that senses the completion of analyte determination bythe test meter. Once apprised of the present disclosure, suitableelectronic modules and software that can accomplish such initiation willbe apparent to those of skill in the art.

Method 700 also includes heating, in response to the initiation step,the shape memory alloy strip from below the solid state transitiontemperature to above the solid state transition temperature, as setforth in step 720 of FIG. 3. The heating of step 720 results in theshape memory alloy strip undergoing a transformation from the deformedconfiguration to a programmed configuration.

At step 730, the method also includes applying a force produced by thetransformation from the deformed configuration to the programmedconfiguration to the test strip and, thereby, ejecting the test stripfrom the test strip receiving port of the test meter.

Once apprised of the present disclosure, one skilled in the art willrecognize that method 700 can be readily modified to incorporate any ofthe techniques, benefits and characteristics of test strip ejectionmechanisms and test meters according to embodiments of the presentinvention and described herein.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that devicesand methods within the scope of these claims and their equivalents becovered thereby.

1. A method for ejecting a test strip from a test meter comprising:initiating activation of a test strip ejection mechanism in apre-ejection state, the test strip activation mechanism including ashape memory alloy strip that exhibits a solid state transitiontemperature and that has a programmed configuration and a deformedconfiguration, wherein in the pre-ejection state a test strip has beenreceived within a test strip receiving port of the test meter and theshape memory alloy strip is in the deformed configuration; heating, inresponse to the initiation step, the shape memory alloy strip from belowthe solid state transition temperature to above the solid statetransition temperature such that the shape memory alloy strip undergoesa transformation from the deformed configuration to the programmedconfiguration, wherein the transformation produces a force; and applyingthe force produced by the transformation to the test strip and therebyejecting the test strip from the test meter.
 2. The method of claim 1further including the steps of: cooling, subsequent to the transferringstep, the shape memory alloy strip from above the solid state transitiontemperature to below the solid state transition temperature.
 3. Themethod of step 2 wherein the cooling is accomplished by naturalconvection in the absence of heating by a heating module of the teststrip ejection mechanism and the shape memory alloy strip is cooled toambient room temperature.
 4. The method of claim 2 further including thestep of: returning the shape memory allow strip to the deformedconfiguration of the pre-ejection state.
 5. The method of claim 1wherein the heating step is accomplished by forcing a current throughthe shape memory alloy strip using a heating module of the test stripejection mechanism.
 6. The method of claim 1 wherein the heating steptransforms the applying step is accomplished via a slider of the teststrip ejection mechanism.
 7. The method of claim 1 wherein the shapememory alloy strip is a shape memory alloy wire.
 8. The method of claim7 wherein the shape memory alloy wire is formed of a Nickel-Titaniumshape memory alloy.
 9. The method of claim 1 wherein the heating stepproduces a force as the shape memory alloy strip transforms from anessentially bowed configuration to an essentially a straight-lineprogrammed configuration.
 10. The method of claim 9 wherein thestraight-line programmed configuration is essentially perpendicular to atest strip ejection direction.